Crash on click when Tweaks/Popup-at-pointer not enabled

Submitted by Tony Paulic @ToZ

Assigned to Mike Massonnet

Link to original bug (#13570)

Description

Running fully updated from the git tree on Arch Linux (all Xfce components are latest git versions).

gtk3: 3.22.14-1

If Tweaks>"Position menu at mouse pointer" is false, left clicking on the panel generates:

(wrapper-2.0:7454): libxfce4panel-CRITICAL **: IA__xfce_panel_plugin_get_screen_position: assertion 'XFCE_IS_PANEL_PLUGIN (plugin)' failed
xfce4-panel(external): xfce4-clipman-plugin-12: child exited with status 139
xfce4-panel-Message: Plugin xfce4-clipman-plugin-12 has been automatically restarted after crash.
xfce4-panel(external): xfce4-clipman-plugin-12: scheduled a respawn of the child
xfce4-panel(external): xfce4-clipman-plugin-12: child is unembedded
xfce4-panel(struts): 0x2077a20: bottom=24, start_x=1075, end_x=1365
xfce4-panel(external): xfce4-clipman-plugin-12: child spawned; pid=10037, argc=8
xfce4-panel(external): xfce4-clipman-plugin-12: child is embedded; 6 properties in queue

...and the plugin crashes. I did a git bisect and the offending commit is https://git.xfce.org/panel-plugins/xfce4-clipman-plugin/commit/?id=55bdffdb1a1f72f913331a00dab387df335568d6.